This invention relates to chain link modular conveyor belts that follow curved paths and chain link modules therefor, and more particularly it relates to chain link belts with each chain link forming a load carrying conveyor platform surface structure module integral with and extending laterally from the chain links to the edges of a belt of predetermined width significantly greater than the chain width.
Chain belts are known that have chain links constructed for bending around curves in a belt path as for example disclosed in U.S. Pat. No. 5,404,997, Apr. 11, 1995 to U. Schreier, et al. for ARTICLE TRANSPORTING APPARATUS INCLUDING INTERCONNECTED CHAIN PART PROVIDED WITH ROLL BODIES, which belt has a load carrying surface only as wide as the chain links.
Some chain conveyor links of the foregoing type have carried load bearing panels with intermeshing leading and trailing tooth structure, wherein the panels extend laterally beyond the chain links to increase the width of the conveyor belt, as disclosed in U.S. Pat. No. 5,489,020, Feb. 6, 1996 to R. T. Clopton for SMOOTH-DRIVING CONVEYOR CHAIN, and U.S. Pat. No. 5,697, 492, Dec. 16, 1997 to P. E. Damkjaer for CONVEYOR CHAIN, wherein the panels abut and interdigitate at zig-zag shaped trailing and leading edges.
U.S. Pat. No. 3,627,109, Dec. 14, 1971, to R. E. Cabak for CONVEYOR CONSTRUCTION discloses a belt where every other chain link comprises a belt width transport panel pivoted between leading and trailing chain links which serve as pivots for permitting belt curvature. This chain is complex requiring expensive roller bearings and accompanying ride-in channel shaped tracks accomodating the chain.
Curved path conveyor chain links are also known in which the load bearing platforms extending laterally from the chain links have upwardly extending ribbed finger platform surface structure serving to overlap and interdigitate with the fingers on trailing or leading modules to form a non-continuous load bearing surface along the length of the belt, as disclosed by U.S. Pat. No. 4,754,872, Jul. 5, 1988 to P. E. Damkjaer for CONVEYER CHAIN LINK. These and other ones of the foregoing belts also tend to induce problems in providing overlapping of modules to provide a substantially continuous load transport surface without intermodule gaps, as required in many conveyor applications.
In U.S. Pat. No. 4,645,070, Feb. 24, 1987 to R. F. Homeier for DUAL BEND CONVEYOR, wherein alternate teeth on one chain link comprise load carrying platform modules forming overlapping and interdigitating teeth on leading and trailing platform module edges. This conveyor has the problem of requiring a standard bicycle like chain construction to be distorted in maneuvering curved paths. Also the chain itself cannot carry heavy transport loads required in many conveyor applications, and has the disadvantage of short lateral extensions because of a cantilevering connection of the platforms to the chain links, as do other ones of the foregoing chain type conveyor belts.
Because of the aforesaid problems, these prior art chain link conveyors have generally been used mainly for conveyor belts of narrow width because of problems such as the ability to carry unbalanced loads or heavy loads near the belt edges. For example, the platforms may tilt in response to unbalanced loads, particularly when supported substantially by the chain links along curved transport paths.
Furthermore, particularly with lighter weight plastic belts, both the ribbed finger structure and the platform structure had to be heavy and rugged to prevent fracture under dynamic belt loading conditions, and have been particularly prone to damage at belt edges where the hinges are apt to encounter flutter, frictional interference and snagging from foreign objects. Nevertheless, it is highly desirable to keep the belt platform structure light while retaining a high degree of resistance to fracture particularly in the belt edge regions at curves, where the loading is the greatest.
In light weight plastic belts having interdigitating finger structure overlapping at leading and trailing edges, there are significant problems of vibration, friction, wear, undue stresses at belt edges when encountering curves, and dynamic stresses in the chain drive links and associated pivot rods which the integrated belt structure of the known prior art systems have not adequately resolved to prevent wear and fracture of the fingers.
Thus it is an objective of this invention to resolve the aforesaid problems in chain link driven conveyor belts of significant width structured to overcome the foregoing problems, particularly when relying upon light weight plastic materials with relatively fragile interdigitating fingertip construction.
It is a particular objective of this invention to provide a long life chain belt which can stably sustain heavy loads along a curved transport path, wherein the belt is low cost and light weight, yet rugged in operation. other objects, features and advantages of this invention will be found throughout the following description, drawings and claims.
This invention provides an improved flexible conveyor belt for transporting goods over curved paths. The belt is formed from interconnected chain link modules integrally carrying conveying surf ace platforms laterally extending therefrom to define a belt of predetermined width. The belt is moved by transport drive means engaging chain links. The modules comprise a laterally extending slat extended across the belt width integrally sandwiched between the chain link and the belt transport surf ace formed of closely spaced rib fingers establishing a substantially planar and continuous conveying surface.
The rib fingers are disposed in two parallel sets of interdigitating rib fingers with finger tips extending beyond the leading and trailing edges of the slats. The two sets are disposed angularly to meet in a V at the belt center to form an apex slanting the finger tips of two rib finger sets on each modular link, thereby to dispose finger tips inwardly at the belt edges for reducing possibilities of interference and fracture.
Substantially Y-shaped chain links with pivot rod apertures in the base leg and two bifurcated arms thus pivotally nest the legs between the arms in a chain. The pivot rod aperture in the chain link legs comprises an elongated slot to provide a predetermined degree of slack in the chain thereby forming a flexible chain which also permits the belt to laterally pivot for passing over curved transport paths.
The slat is affixed integrally to the chain links to extend toward two edges of the belt from the chain links. An upper conveying belt surface is integrally formed on the slats for overlapping trailing and leading chain link modules. The conveying surface section carried by each modular link overlaps trailing and leading slat edges by interdigitating the raised rib fingers. A substantially planar and continuous platform surface thus is formed.
A substantially solid elongated slat panel has a somewhat truncated diamond shape. Thus, the slats present at trailing and leading edges rocker apexes protruding at midbelt positions and therefrom diverge inwardly forming on each side of the apexes angularly disposed substantially straight leading and trailing edges. Under tension for a straight belt path, the apexes are spaced a short distance apart by means of the pivot rod movement in the slotted aperture of the Y-chain link leg. For curved belt paths the apexes meet to provide a rocking center thus permitting slats to move closer together on an inner side of a curve and further apart on the outer side of a curve. The two diverging straight line slat edges thus abut in mating contact on an inner curvature side of the slat at a maximum curvature radius.
In a preferred embodiment, successive chain link modules have enough play between the mated leg and arm structure when linked together by a pivot rod through the slotted leg aperture, that permits a degree of lateral pivoting of the belt as it is transported about a curved path. Two or more chains preferably share the drive load since the slat is disposed across two spaced apart chain links. Thus a much wider belt width for carrying heavier loads is attainable with light weight plastic chain link modules.
For strengthening the edge portion of the belt and for permitting thin, light weight plastic rib fingers to be used in the platform with less danger of being fractured at the belt edges which endure the greatest abuse, the slat at the belt edges has toothed structure shortening rib fingertips that extend away from the slat edge. These fingertips may in some embodiments be of uniform length across the width of the belt. However in one embodiment at the belt edge regions where the fingers are more subject to interference and fracture, the slat end regions are configured with mating tooth-notch structure at leading end trailing slat edges. Resulting shorter finger tips reduce finger tip vibration, wear and the possibility of fracture. At the tooth-notch slat structure, the tooth of one slat thus abuts and mates into the mating edge notch of an adjacent slat in mating registration when the slats abut on the inner curvature of the belt. The thin rib fingers overlap the slat structure leading and trailing slat edges far enough to interdigitate with mating rib fingers on adjacent leading and trailing slat edges both in straight and curved travel paths over the width of the belt. Thus unsupported spots are eliminated and the load is supported in part by slats upon which the fingertips ride. Furthermore, this structure assures that small items cannot fall through or snag the belt, where they can cause catastrophic failure.
Typically for one embodiment of a plastic belt the ribs are about {fraction (1/16)}th inch thick and xc2xc inch high, slats about xc2xc inch thick and about 24 inches long, with two chain links disposed integrally on the slats about eight inches apart and eight inches from opposite belt edges.
The belt is supported along its length and rides upon a wear pan sheet typically having at least a contact surface of low friction plastic such as UHMW (ultra-high molecular weight) supported by suitable framework. Preferably guard rails at the edges also protect the fingers at the edges of the belt from snagging foreign objects, and serve to prevent relative side-to-side movement of the modules in the adjacent rows, thus restricting frictional interference during normal belt operation.
In another embodiment, the belt includes a series of cavities formed in the slats with rollers rotatably received in the cavities. A salient portion of the rollers extends above the slats to coact with conveyed articles in rolling contact.
Other features and advantages will be found in the following more detailed description and accompanying drawings.